how much blow-by is too much ?....

[Northern Wrangler 6.2]

So, on top of no tach working, and engine lite on, my new gem has what appears to be a fair bit of blow-by, out the oil filler and dipstick tube. At 190,000 miles, should I look for anything or is the motor likely pooched ? It starts and runs well, sounds good, just looks like it's worn out by the amount of blow-by. Will a bad CDR valve cause any of this ?

What else should I consider on this rig, it looks like the PMD is in stock postion, with no heat-sink, I know this needs to be done.

Any advice will be well recieved.

Thanks group.

Kev

[john8662]

Drive it and see what happens to the blow-by. Has it been sitting for a long time prior to you taking posession?

[jspringator]

Can a dirty air filter increase blowby?

[Bnave95]

6.2 with a PMD? or a reinstalled 94 + 6.5 turbo?
CDR could use a cleaning and vaper from oil fill is normal unless it's coming out like a steam eng. chug,chug,chug:)

[Hubert]

Can a dirty air filter increase blowby?

A dirty air filter will increase vaccum on the cdr/crankcase. So what if really dirty it pulls too much on CDR it might regulate closed and then the the crankcase would build pressure and smoke more out of filler tube? A slightly dirty air filter I think would mask blowby vapors by drawing more on crankcase.

Is that what you mean?

[HH]

Could do a compression check to rule out bad rings or cracked piston. Mine had blow by, and later a completely cracked piston.

[BobND]

A dirty air filter will increase vaccum on the cdr/crankcase. So what if really dirty it pulls too much on CDR it might regulate closed and then the the crankcase would build pressure and smoke more out of filler tube? A slightly dirty air filter I think would mask blowby vapors by drawing more on crankcase.

Is that what you mean?


One side of the CDR's diaphragm is exposed to the atmosphere, the other to the crankcase side of the CDR. There is a light coil spring holding the CDR fully open, and it doesn't even begin to close until the crankcase pressure is NEGATIVE... below atmospheric pressure by the amount of spring tension in relation to the area (size) of the diaphragm.

So, even with a restricted air filter the CDR is not going to be closing AT ALL as long as the the crankcase pressure remains higher then the NEGATIVE value set by the CDR's spring.

[Northern Wrangler 6.2]

John: It was sitting for almost 8 months before I picked it up. It drove home 4 hours without any ill running. Tach is not working, check engine light comes on. Maybe I'll check it over and drive it a few days, just to see how it works. I'll do an oil change and swap in a new air filter. Looks like it's been well used, but seems to work ok for the miles. maybe it's not as bad as I expected. We'll see.......

tHanks

[john8662]

Since you're doing an oil change, I'd suggest a full flush.

Use the over-the-counter stuff, or pour in 1 qt diesel fuel into the crankcase (if it's 1 qt low already, if not, correct). Run for 10 minutes idle, then drain, replace filter.

If you've got some sticking rings, etc., this will help.

J

[Mark Rinker]

My '94 was burning 1 quart per 1,000 and showing lots of blow-by.

1) Replace CDR
2) Switched to synthetic oil
3) Turned down boost pressure.

Oil consumption dropped to 1 quart per 3,000. Acceptable in my book.

[6.5stayingalive]

Just wanted to let 6.5 drivers that I have a 1994 6.5 turbo diesel, electric not mechanical with almost 500000k on it ...strated to notice blowby, with that being said I thought the engine was going. ....it was smoking badly through the oil fill and dip stick .....found out it was a bad wire from the crank sensor. ...replaced the wiring and no more blowby! Truck is running great!

[svcattle]

How did the crank sensor affect blow buy ? My truck has developed a lie of blow buy runs fine I think I had a couple dirty injectors I've been running stanadyne with every tank and the truck idles a lot better now but stil a massive amount of blow buy

[phantom309]

Crank sensor>>>blowby,..

Thats a new one on me,.

My old 94 is huffing pretty good when it's hot,. i,ve been venting it to atmosphere for a couple of years now to cut down the oil leaks,.
It also has a 5068 pump on it with a custom chip that puts boost levels waay over what people are comfortable with here,.it really could use a much bigger turbo,.
it doesn't overheat, starts great,.a/c works great,every steering component/knuckle is worn out, brakes and tires are still good,

Meh,. I'll just drive on, and leave the crank sensor alone,.:cool: